The 21-year-old was advised to move to Love Street by former Buddies loanee Esmael Goncalves.
"Stephane is a striker, 6ft 2ins, powerful and quick. He's made 22 appearances for Nice and got four goals," St Mirren boss Danny Lennon told reporters. "He's the one we've been waiting for, but I believe he's been worth the wait.
"We've been under no illusions that a striker is what we needed to give Stevie Thompson and Gary Harkins a hand up there. But we think we have identified the right one who will come in and give us exactly what we need.
"Esmael Goncalves, who we had here last season, was quite influential in telling Stephane about his experience here and how it helped his career. That was lovely of him to do."
Bahoken could make his debut against Partick Thistle this afternoon.